The present invention pertains generally to ceramic material processing and in particular to the processing of ferroelectric materials.
Ferroelectric materials are dielectric materials with domain structure, which exhibit spontaneous electric polarization. These materials possess relative permittivities of up to 10.sup.5 and show dielectric hysteresis. Ferroelectric materials are often excellent piezoelectric material, i.e., giving rise to electric polarization when subjected to mechanical strain or producing mechanical deformation when subjected to an applied electric field.
Lead titanate is an example of such a material. Unfortunately, lead titanate, upon cooling through the Curie temperature after the powder has been sintered to a ceramic, loses strength and structural integrity. To correct this problem, additives e.g. zinc oxide, manganese dioxide, and sodium carbonate are included with the lead titanate (PbTiO.sub.3). The strength of the resulting materials is typically from 5000 to 7000 psi and the density is from 85 to 95 percent of the theoretical density. Although these strengths and densities are significant improvements, the additives are objectionable on account of the modification of the chemical composition which results in a reduction of the dielectric constant and coupling factor and in an interference with the effectiveness of other additives to densify, lower process temperatures, or modify the microstructure.